President Dmitry Medvedev has opened his account on the Twitter microblogging service and sent his first tweets while visiting the Twitter headquarters in California’s Silicon Valley.Twitter users can follow the Russian president on Twitter at KremlinRussia (in Russian) and KremlinRussia_e (in English)."Hello everyone! I'm on Twitter, and this is my first tweet", Medvedev typed.In his next tweet the Russian president shared his impressions of the trip and talked about his plans. “San Francisco is a very beautiful city. Heading to Silicon Valley today to visit Apple, Yandex and Cisco,” he continued.